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İSPİRLİ, MEHMET MURAT

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İSPİRLİ

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MEHMET MURAT

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    PublicationOpen Access
    The effect of water on tracking failure of epoxy/MgO samples
    (2022-12-01) İSPİRLİ, MEHMET MURAT; Kirkagac K., İSPİRLİ M. M., Ersoy A.
    In this study, the change in the electrical performance of epoxy/MgO, which is one of the materials used to increase the performance of epoxy resin, was evaluated under the effect of water. Accordingly, comparative tracking index (CTI) experiments, which are one of the effective methods used to model electricity\"s effect on surface properties, were used. To measure the performance of epoxy resins without additions, 1%, 3% and 5% nanosized MgO-added samples were prepared. Prepared samples were stored 24 h, 48 h, 72 h, 96 h and 120 h in pure water. Then, the samples were subjected to CTI test in a laboratory environment. Recorded leakage current from experiments was analyzed using harmonic analysis. While the experimental results obtained have resulted in improvements like those of MgO/epoxy additions previously reported in the literature, the resistance of the observed samples after their exposure to pure water has been reported, in the opposite direction. Thus, with this experimental study, it has been demonstrated that it is necessary to add some hydrophobic compounds to show the desired performance in the external environment with MgO-doped epoxy resins. It should be supported by extra protection in such dense liquid environments.
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    PublicationOpen Access
    The effect of dc voltage pre-stress on the breakdown voltage of air under composite dc and li voltage and test circuit: Design and application
    (2022-02-01) İSPİRLİ, MEHMET MURAT; ORAL, BÜLENT; İSPİRLİ M. M., Kalenderli Ö., Seifert F., Rock M., ORAL B.
    © 2022 by the authors. Licensee MDPI, Basel, Switzerland.The use of HVDC systems is increasing in number due to technological innovations, increasing power capacity and increasing customer demand. The characteristics of insulation systems under composite DC and LI voltage must be examined and clarified. In this study, firstly, experimental circuits were designed to generate and measure composite DC and LI high voltage using a simulation program. The coupling elements used were chosen according to simulation results. Afterward, experimental circuits were established in the laboratory according to the simulation results of the designed experimental circuit. Then, breakdown voltages under composite DC and LI voltage for less uniform and non-uniform electric fields were measured with four different electrode systems for positive and negative DC voltage pre-stresses with different amplitudes. The 50% breakdown voltage was calculated using the least-squares method. Finally, 3D models were created for the electrode systems used in the experiments using the finite element method. The efficiency factors of electrode systems calculated with the FEM results were correlated with the experimental breakdown voltage results. Thus, the breakdown behavior of air under bipolar and unipolar composite voltages (CV) was investigated. In conclusion, the experimental results showed that very fast polarity change in bipolar CV causes higher electrical stress compared to unipolar CV.